Process for the separation of long chain amino acids and dibasic acids

ABSTRACT

There is disclosed a process for the separation of long chain amino acid and long chain dibasic acid, comprising: (1) adding water and an extractant solvent to the aqueous suspension of an acid hydrolysis of the mixed amide derivatives to yield an aqueous solution and an extractant phase; (2) separating the mixture of step (1) into an aqueous phase containing the acid salt of long chain amino acid and alkylamine and an extractant phase containing long chain dibasic acid, short chain alkanoic acid, and impurities; (3) neutralizing the aqueous phase of step (2) with a basic agent to obtain a crystalline suspension of the long chain amino acid; (4) recovering the long chain amino acid by solid-liquid separation to yield an aqueous mother liquor; and (5) in the extractant phase of step (2), separating the long chain dibasic acid, short chain alkanoic acid, and impurities.

CROSS REFERENCE

This application is a continuation of the co-pending application Ser.No. 15/635,874, filed on Jun. 28, 2017, the entirety of which isincorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a process for the separation of longchain amino acids, dibasic acids, short chain alkylamines, and alkanoicacids.

BACKGROUNDS OF THE INVENTION

Long chain saturated aliphatic amino acids, lactams, and dibasic acidsare important monomers for long chain nylons and engineering plastics.Nylons are a class of polymers that contain amide bond on their backboneof chains. Nylons are one of the most widely used, most numerous intypes, and most consumed class of engineering plastics.

Because of their unusual molecular structure, long chain nylons possessextraordinary physical properties, i.e., higher mechanical strength thanmetal, low hygroscopicity, excellent resistance to oil, low temperature,abrasion, and chemical corrosion, and most importantly, easy tofabricate. Long chain nylons are made into many kinds of plasticsproducts, spun to fibers, and stretched to thin films. Long chain nylonsare also used in paints and hot melt adhesives. Hence, long chain nylonsfind wide applications in automobile, electrical, electronic,telecommunications, petrochemical, and aerospace industries.

Long chain amino acids and lactams are used industrially as monomers toproduce nylon-9, nylon-11, and nylon-12.

Long chain dibasic acids are condensed with diamines industrially asstarting materials to produce nylon-610, nylon-612, nylon-510,nylon-512, nylon-1010, and nylon-1212.

WO 2017/088218, the co-pending U.S. Ser. No. 15/601,556, and U.S. Ser.No. 15/617,268, all of which by the present inventor, all of which areincorporated by reference herein, disclose a novel process for thecoproduction of long chain amino acids and dibasic acids from keto fattyacid derivatives. According to the disclosed process, long chain ketofatty acid derivatives are reacted with hydroxylamine to form an oximederivative, which is subjected to the Beckmann rearrangement to yield amixture of two amide derivatives. These amide derivatives are hydrolyzedto a mixture of products containing long chain amino acids and dibasicacids, which are isolated by a process of step-wise neutralization in ahighly dilute concentration. Thus, a substantial amount of energy isrequired for the concentration, so that the process is not economical.

Moreover, the present inventor has found that long chain amino acids anddibasic acids of required quality for the production of polyamidescannot be obtained, if the process according these prior disclosures isapplied for commercial starting materials, which contain various amountof other fatty acids. Apparently, these impurities contaminate intendedproducts and thus demand a process for their removal from final productsof required purity.

Hydrolysis of the mixed amide derivatives from the Beckmannrearrangement yields not only long chain amino acids and dibasic acids,but also short chain alkyl amines and alkanoic acids. There is a lack ofany method for the separation and recovery of these short chain productsfrom the mixture of the hydrolysis reaction.

It is desirable to have a process for the separation of each componentto their required purity from their complex mixture to achieve aneconomical process and to reduce or eliminate the disposal of wastestream.

It is an object of the present invention to disclose a process for theseparation of long chain amino acids, dibasic acids, short chain alkylamines, short chain alkanoic acids, and for the recovery of other fattyacids present in the commercial starting materials, such as stearicacid, and impurities generated as byproducts of the productionreactions. By the process of the present invention, long chain aminoacids and dibasic acids are separated simply, efficiently, andeconomically with high yields and excellent purity.

It is another object of the present invention to disclose a process forthe recovery of long chain amino acids and inorganic salts from aqueouswaste mother liquor. As a result, there is no waste discharge fromproduction process.

DESCRIPTION OF THE DRAWINGS

FIG. 1. Schematic flowchart for the separation of long chain amino acid,dibasic acid, alkylamine, and alkanoic acid from their mixture in thecase of an alkali hydroxide hydrolysis.

FIG. 2. Schematic flowchart for the separation of long chain amino acid,dibasic acid, alkylamine, and alkanoic acid from their mixture in thecase of an acid hydrolysis.

FIG. 3. Schematic flowchart for the recovery of long chain amino acidand alkali salt from waste aqueous stream with the aid of an alkalihydroxide.

FIG. 4. Schematic flowchart for the recovery of long chain amino acidand alkali salt from waste aqueous stream with the aid of an acid.

FIG. 5. Schematic flowchart for the treatment of aqueous stream torecover alkylamine, long chain amino acid, and alkali salt for an acidhydrolysis of mixed amide derivatives.

FIG. 6. Solubility curve of 11-aminoundecanoic acid in water at neutralpH, 1 M solution of sulfuric acid, and 2 M solution of sodium hydroxide.

DESCRIPTION OF THE INVENTION

Hydrolysis of the mixed amide derivatives of the following structures:

from the Beckmann rearrangement of oxime fatty acid derivatives can becarried out with either an acid or a base to yield a mixture of mainproducts of the following structures:

wherein m is an integer from 0 to 10, n is an integer from 6 to 20; X isOR or NR₁R₂, wherein OR is OH, C₁-C₈ monohydric alcohol or C₁-C₈polyhydric alcohol, and R₁ and R₂ are each independently hydrogen orC₁-C₈ alkyl group.

When m=5, n=10, the main products are 11-aminoundecanoic acid,dodecanedioic acid, hexylamine, and heptanoic acid. Because the startingmaterial of commercial grade is obtained from castor oil, significantamount of stearic acid is also present as an impurity in the mixture ofproducts.

When m=7, n=8, the main products are 9-aminononanoic acid, sebacic acid,octylamine, and pelargonic acid.

When m=5, n=12, the main products are 13-aminotridecanoic acid,tetradecanedioic acid (brassylic acid), hexylamine, and heptanoic acid.

When the hydrolysis reaction of mixed amide derivatives from theBeckmann rearrangement is performed in the presence of alkali hydroxide,main products other than alkylamine are obtained in the form of theiralkali salts. It was observed that a starting suspension of the mixedamide derivatives in a solution of alkali hydroxide is changed to aclear solution at a temperature of 60° C. or above after the hydrolysis.Upon cooling, the clear solution becomes a pasty, non-stirrable cake,because alkali salts of long chain amino acids and dibasic acids arenearly insoluble in an alkali solution as shown in FIG. 6.

The alkali metals are lithium, sodium, potassium, or cesium.

The process according to the present invention, illustrated in FIG. 1for the separation of each component in a mixture of the hydrolysisreaction by the method of alkali hydroxide, starts with removal oflow-boiling components and alkylamine.

The low boiling component comes from alcohols, i.e., methanol orethanol, commonly used in the starting material of keto fatty acidesters. If the mixed amide derivatives are carboxylic acid, little or nolow boiling component is present in the mixture.

These low boiling alcohols, formed by the hydrolysis of esters, aredistilled off from the reaction mixture. Distillation of these lowboiling alcohols can be carried out under normal pressure, increasedpressure, or reduced pressure, during or after the hydrolysis reaction.

Some alkylamines, in particular, of C₁ to C₅, are of lower boilingpoint, and they are distilled off along with alcohols. These alkylaminescan be separated from alcohols according to methods known in prior art.

For the production of 11-aminoundecanoic acid and dodecanedioic acid,hexylamine is one of the main products. Hexylamine is found to form anazeotrope with water and can be separated from the solution byazeotropic distillation. Upon cooling, the distillate separates into anupper phase of nearly pure hexylamine and an aqueous phase containingnot more than 2% of hexylamine. Hexylamine can also be separated fromthe mixture by steam distillation or steam stripping. Completeseparation is accomplished when the distillate at the overhead becomesnearly neutral at a pH of 7-8.

The hexylamine distillate contains a small percentage of water and canbe dried with a drying agent, and preferably, by azeotropic distillationof a small amount of hexylamine to remove the water in hexylamine.

Hexylamine and alkylamines of more than C₇ can also be separated fromthe hydrolysis solution by extraction with an extractant solvent. Thesealkylamines show excellent partition properties between an organicextractant phase and the strongly alkaline aqueous mixture of thehydrolysis reaction. Suitable extractant solvents are selected from theclasses of ester, aliphatics, aromatics, ethers, ketones, andwater-insoluble amines. Preferably, selected extractant solvent is thesame as the solvent chosen for the next stage of the process accordingto the present invention.

Long chain amino acids and dibasic acids exhibit similarly lowsolubility through a wide range of pH from 2 to 10 at room temperature.Their separation from each other necessitates a high dilution with greatdifficulty even when their mixture is not contaminated by otherimpurities of similar properties, such as fatty acids. When thecommercial starting materials, which invariably contain many other fattyacids, are used in the process according to previous disclosure, theproducts, long chain amino acids and dibasic acids, are alwayscontaminated with these fatty acids.

The present inventor carried out extensive studies to overcome theinherent problems imposed by their little difference in solubility forlong chain amino acids and dibasic acids and found in the presentinvention that the solubility of long chain amino acids can be greatlyincreased by reacting these amino acids with an acid to form an acidsalt at increased temperature. At the same time, alkali salts of longchain dibasic acids and fatty acids in the solution are turned intotheir free carboxylic acids, which can be dissolved in an organicsolvent. Complete separation of these long chain amino acids from longchain dibasic acids and fatty acids is thus accomplished by forming anaqueous solution of an acidic salt of these long chain amino acids andan organic extractant phase rich in long chain dibasic acids, shortchain alkanoic acids, and fatty acids.

Suitable acids are an acid of a pKa<5.0. These acids are, but notlimited to, inorganic acids, i.e., hydrochloric acid, hydrobromic acid,hydroiodic acid, sulfuric acid, nitric acid, phosphoric acid; alkyl andaryl sulfonic acids, i.e., methanesulfonic acid, ethanesulfonic acid,propanesulfonic acid, isethionic acid, benzenesulfonic acid,toluenesulfonic acid, xylenesulfonic acid, and sulfamic acid; organiccarboxylic acids: malic acid, maleic acid, tartaric acid, glycolic acid,lactic acid, citric acid, oxalic acid, formic acid, acetic acid, andpropionic acid. One or a mixture of two or more of these acids can beused to form an acidic salt of long chain amino acids.

Preferably, the acid is selected from one of the inorganic acids, andmost preferably, sulfuric acid.

The aim of acidification is to completely convert alkali salts of longchain dibasic acids, short chain alkanoic acids, and fatty acids intofree carboxylic acids and to form an acid salt of long chain amino acid,so as to ensure complete dissolution of long chain amino acid in aqueousphase and long chain dibasic acid in an organic extractant phase.

Organic solvents suitable for extracting dibasic acids and fatty acidsare water-insoluble and belong to the classes of ester, aliphatics,aromatics, ethers, alcohols of C₄ to C₁₀ and ketones of C₄ to C₁₀.Useful solvents include, but not limited to, butyl formate, isobutylformate, butyl acetate, isobutyl acetate, propyl acetate, isopropylacetate, ethyl acetate, ethyl propionate, octyl acetate, benzene,toluene, xylene, cumene, anisole, diethyl ether, diisopropyl ether,dibutyl ether, methyl tert-butyl ether, ethyl tert-butyl ether, methyltetrahydrofuran, petroleum ether, cyclohexane, dichloroethane, methylenechloride, chloroform, carbon tetrachloride, and trifluoromethylbenzene,n-butanol, isobutanol, amyl alcohol, isoamyl alcohol, hexanol,cyclohexanol, 2-ethylhexanol, isooctanol, sec-octanol, butanone,pentanone, hexanone, cyclohexanone, methyl isobutyl ketone. A singlesolvent or a mixture of two or more solvents can be used as extractantsolvent.

Selected extractant solvent is expected to have good solubility of longchain dibasic acid and fatty acid at higher temperature, low or littlesolubility at lower temperature for the long chain dibasic acid and goodsolubility for fatty acid or the like at lower temperature to ensure aneffective separation of long chain dibasic acid from other fatty acidsrich in the organic phase.

Preferably, the extractant solvent is toluene.

The amount of extractant solvent is not limited, but is greater than theeffective amount for the dissolution of dibasic acids and fatty acidimpurities.

Temperature to perform acidification and extraction is in the range from50° C. to the boiling point of the mixture of extractant organic phaserich in long chain dibasic acid and fatty acid and below 100° C. undernormal pressure. Acidification and extraction can also be carried out atelevated temperature under pressure, but pressure equipment will beneeded for the process.

Preferably, acidification and extraction are performed at a temperaturefrom 60° C. to 95° C., and most preferably at a temperature from 80° C.to 90° C. At higher temperature, the higher solubility of long chaindibasic acid in the extractant solvent is advantageous in reducing theamount of the extractant solvent used.

There is no preference as to how an acid and an extractant solvent areintroduced into the solution of alkali salts of long chain amino acidand dibasic acid that have been freed of alkylamine. An acid and anextractant solvent can be added concomitantly, sequentially,continuously, semi-continuously, or batch wise.

When the acidification and extraction are performed according to theprocess of the present invention, good phase separation is achieved. Thepresent inventor unexpectedly found that extractant solvent extractsnearly all colored materials into extractant phase, leaving behind acolorless aqueous solution of the acid salt of long chain amino acid,which provides an added advantage in greatly simplifying thepurification of long chain amino acids.

The present inventor found that a middle phase between the upperextractant phase and lower aqueous phase is formed in some cases andcontains predominantly the acid salt of long chain amino acid and theacid salt of hexylamine, if hexylamine is not removed or removedincompletely from the hydrolysis solution. This middle phase is formed,especially, when the aqueous solution contains a high concentration ofalkali salt. However, the middle phase can be effectively separated andcombined with aqueous phase to recover long chain amino acid.Alternatively, after separating the aqueous phase, the middle phase isdissolved with deionized water at increased temperature.

Although the aqueous solution of the acid salt of long chain amino acidis nearly colorless, to further improve the quality of the isolatedproduct, the solution can be treated with activated carbon to decolorizeand to absorb minor impurities. The treatment can be carried out from50° C. to the boiling point for a period from a few minutes to a fewhours, preferably 30 minutes to 2 hours, most preferably for 1 hour.After filtration, a clear colorless solution is obtained.

In order to isolate long chain amino acid, the strongly acidic aqueoussolution is neutralized with a basic agent to near neutral acidity in apH range from 5 to 9. More preferably, the pH is in the range of 6 to 8.The neutralization is performed at a temperature from 50° C. to theboiling point of the solution, preferably from 60 to 90° C., mostpreferably from 70° C. to 80° C. Neutralization at this most preferredtemperature produces larger crystals that will facilitate solid-liquidseparation. After cooling to 30° C. to 40° C., the product, long chainamino acid, is precipitated and separated by means of solid-liquidseparation, i.e., filtration or centrifuge, to yield a mother liquorcontaining inorganic salt and a small amount of long chain amino acid.

The basic agent is selected from the group consisting of ammonia, alkaliand ammonium salts of hydroxide, bicarbonate, carbonate, sulfite,bisulfite, and carboxylate. A single agent or a mixture of two or moreagents can be used. Preferably, the basic agent is an alkali hydroxide,and most preferably, the same agent used in the hydrolysis reaction ofthe mixed amide derivatives.

The most preferable basic agent is sodium hydroxide.

Treatment of the mother liquor after the isolation of long chain aminoacid is illustrated in FIG. 3 and FIG. 4 to achieve a completeseparation of inorganic salt and full recovery of long chain amino acidwith the aid of an alkali hydroxide or an acid, respectively.

Since long chain amino acid, e.g., 11-aminoundecanoic acid, hasrelatively constant solubility, evaporative concentration of the motherliquor will result in the crystallization of inorganic salt, inparticular, sodium sulfate, along with valuable long chain amino acid.To overcome this difficulty, the present inventor found that thesolubility of 11-aminoundecanoic acid can be drastically increased byincreasing or lowering the pH at increased temperature as illustrated inFIG. 6. In fact, alkali salt of 11-aminoundecanoic acid becomes freelysoluble in 2 M solution of sodium hydroxide at about 50° C. This findinggreatly facilitates the separation of inorganic salt, most preferably,sodium sulfate, and the recovery of long chain amino acids.

Although the solubility of long chain amino acid can be increased byboth an acid and an alkali hydroxide, it is preferable to use an alkalihydroxide, because alkali salt is non-corrosive to commonly used processequipments made of stainless steel.

After adjusting pH of the aqueous stream with an alkali hydroxide, themother liquor is concentrated to crystallize inorganic salt, mostpreferably, sodium sulfate, at a temperature from 40° C. to the boilingpoint of the solution. Evaporative crystallization can be carried outunder normal, reduced, or increased pressure, continuously or in batch.The crystallized salt is removed from the saturated solution by means ofsolid-liquid separation, e.g., filtration or centrifuge.

The basic mother liquor after removal of alkali salt is acidified withan acid to a neutral pH. The dissolved long chain amino acidprecipitates and can be recovered by means of solid-liquid separation,and the mother liquor is recycled.

The acid used in this step can be selected from the class of inorganicacids, organic carboxylic acids, organic sulfonic acids, sulfamic acid.Preferably, one of the inorganic acids is selected. More preferably, thesame acid is used as in previous step. Most preferably, the acid issulfuric acid.

The extractant phase rich in long chain dibasic acid, short chainalkanoic acid, and fatty acid after the separation of aqueous phase iscooled to a lower temperature in the range of 0° C. to 50° C., morepreferably 0° C. to 30° C., most preferably 10° C. to 20° C. tocrystallize long chain dibasic acid, which can be separated by means ofsolid-liquid separation. Although the extractant phase and filtrationmother liquor is dark in color, the product is nearly white in color andfree of any other fatty acids, such as stearic acid.

The mother liquor is distilled to recover extractant solvent and theresidual is distilled under vacuum to recover short chain alkanoic acid,e.g., heptanoic acid, in nearly pure form.

In one embodiment of the present invention, the extractant phase isfirst concentrated by distillation, then cooled to crystallize longchain dibasic acid in an increased yield.

In another embodiment of the present invention, the extractant phase isfirst distilled to recover extractant solvent, then distilled undervacuum to recover short chain alkanoic acid. To the distillationresidual is added an organic solvent to dissolve the residual byheating, then to crystallize long chain dibasic acid by cooling. Thesolvent is most preferably the original extractant solvent, so that nomixture of different solvents will result to simplify the overallprocess.

In a further embodiment of the present invention, the extractant phaseis distilled to recover solvent and the residual is added to a loweralcohol, in particular methanol or ethanol, most preferably, methanol,in the presence of an esterification catalyst to yield a mixture ofmethyl esters of alkanoic acid, long chain dibasic acid, and other fattyacid originating from starting materials. These methyl esters are thenfractionally distilled to obtain each component in pure form and arefreed of any colored materials. These pure methyl esters are marketeddirectly or can be hydrolyzed to their respective carboxylic acidaccording to process known in prior art.

Alternatively, the mixture of methyl esters is distilled to a mixturethat is freed of any colored materials. The distilled mixture of methylesters are then hydrolyzed to a mixture of alkanoic acid, long chaindibasic acid, and fatty acid, which can be separated according to theprocess of the present invention.

In the case of producing 11-aminoundecanoic acid and dodecanedioic acidaccording to the process of the present invention, the distillationresidual is black in color and contains stearic acid from the startingmaterial of castor oil and a small amount of dodecanedioic acid. Thisdark residual is reacted with a lower alcohol, most preferably,methanol, in the presence of an acid catalyst to form methyl esters. Themixed methyl esters are fractionally distilled to yield colorless methylesters of stearic acid and dodecanedioic acid. The recovered methylstearate is either hydrolyzed to stearic acid or marketed as acommercial product, while the methyl ester of dodecanedioic acid ishydrolyzed to obtain dodecanedioic acid.

When the hydrolysis reaction of mixed amide derivatives from theBeckmann rearrangement is performed with an acid, most preferably,sulfuric acid, alkyl amine and long chain amino acid are obtained in theform of their acid salts, while long chain dibasic acid and fatty acidexist in the form of free carboxylic acid.

After the hydrolysis reaction proceeds to completion, water and anextractant solvent are introduced into the suspension to dissolve theacid salts of long amino acid and alkylamine and to transfer the longchain dibasic acid, short chain alkanoic acid, and other fatty acid intoan extractant phase.

There is no preference as to how water and extractant solvent are addedto the hydrolysis mixture. They can be added concomitantly,sequentially, continuously, semi-continuously, or batch wise. The amountof water added to the reaction mixture is sufficient to effectivelydissolve the acid salts of long chain amino acid and alkylamine. Theextractant solvent is selected on the same principle as described in theprevious section for the extractant solvent for the hydrolysis solutionwith alkali hydroxide.

After dissolution and extraction according to the process of presentinvention, the aqueous phase containing the acid salts of long chainamino acid and alkylamine and the extractant solvent phase rich in longchain dibasic acid and short chain alkanoic acid are separated. An addedadvantage of the present invention is that all colored materials aretransferred into organic extractant phase and the extracted aqueoussolution of long chain amino acid and alkylamine is nearly colorless.

After phase separation, the organic extractant phase is treated in thesame way as for the extractant phase obtained from acidification andextraction of the hydrolysis solution using alkali hydroxide.

The strongly acidic aqueous phase is neutralized with a basic agent to aneutral pH in the range of 5 to 9, more preferably 5 to 8, mostpreferably 6 to 7, to precipitate long chain amino acid. After cooling,the precipitated solid is isolated by means of solid-liquid separation,i.e., filtration or centrifuge.

The basic agent is selected from ammonia, alkali and ammonium salts ofhydroxide, bicarbonate, carbonate, bisulfite, sulfite, and carboxylate.Preferably, the basic agent is alkali hydroxide or ammonium hydroxide,and most preferably, sodium hydroxide.

The mother liquor obtained after the isolation of long chain amino acidcan be treated according to the scheme illustrated in FIG. 5 to separatealkylamine, inorganic salt, and to recover dissolved long chain aminoacid.

When sodium hydroxide is used as the basic agent to neutralize sulfuricacid, more sodium hydroxide is added to the mother liquor to a basic pH,alkylamine can be extracted with an extractant solvent, or preferably byazeotropic distillation. After complete removal of alkylamine, thesolution is further evaporated to separate inorganic salt, preferably,sodium sulfate. Long chain amino acids can be recovered by adding anacid to adjust the pH to neutral.

If ammonia or ammonium hydroxide is used as the basic agent toneutralize sulfuric acid, and after more basic agent is added to themother liquor to a basic pH, alkylamine can only be recovered byextraction. Distillation of the basic solution will remove ammoniainstead of alkylamine.

The process according to the present invention achieves a completeseparation of each component in the coproduction of long chain aminoacids and dibasic acids without discharging any waste aqueous streamfrom the process.

EXAMPLES

The following examples illustrate the practice of this invention but arenot intended to limit its scope.

Example 1

This example relates to the separation of 11-aminoundecanoic acid,dodecanedioic acid, hexylamine, heptanoic acid, and stearic acid fromtheir mixture obtained from sodium hydroxide hydrolysis of the mixedamide derivatives.

A mixture of the starting solution was obtained by hydrolyzing 150 g ofthe mixed amide derivatives prepared from methyl 12-ketostearateaccording to WO2017/088218 with 60 g of sodium hydroxide in 800 mL ofwater.

The solution was azeotropically distilled with a 2.5×30 cm vacuumjacketed column packed with porcelain berl saddles, first to obtainmethanol, then an azeotrope of hexylamine-water until the pH of theoverhead became neutral at a pH of 7-8. The distillate was separatedinto two phases and the lower aqueous phase was continuously returned tothe distillation flask. The crude hexylamine was dehydrated byazeotropic distillation to yield 20.5 g of hexylamine.

To the residual solution were added 800 mL of toluene, followed by 100 gof sulfuric acid. The mixture was vigorously stirred for 60 minutes at85° C. and transferred to a separatory funnel to separate the aqueousphase. The dark-colored upper toluene phase was washed with hotdeionized water and the washing was combined with the aqueous phase.

To the colorless aqueous phase was added 1.0 g of activated carbon andstirred at 80° C. for 45 minutes and the solution was filtrated toobtain a clear, colorless solution. The solution was neutralized with asolution of sodium hydroxide to a pH of 7.5 at about 70° C. to yield acrystalline suspension. After cooling to 35° C., the suspension wasfiltrated and the solid material washed three times with deionizedwater. After drying, 42.5 g of white 11-aminoundecanoic acid wasobtained.

To the mother liquor of about 1200 mL was added 1.0 g of sodiumhydroxide. The solution was concentrated and sodium sulfate removed byfiltration three times so that 300 mL of solution remained. This basicsolution was adjusted with dilute sulfuric acid to a pH of 7.5 torecover another 0.8 g of 11-aminoundecanoic acid.

The toluene solution was washed with hot deionized water once and cooledon ice to 5° C. to obtain a crystalline suspension. After filtration,washing with cold toluene, and drying, 45.2 g of dodecanedioic acid wasobtained. The product was off-white.

The toluene filtrate was combined with toluene washing and distilled torecover toluene. The residual was then vacuum distilled with a shortpath column to yield 24.5 g of heptanoic acid.

The residual after distillation was black and weighted 26.6 g. Theresidual was mixed with 200 mL of methanol and added 1.0 g of sulfuricacid. After the mixture was refluxed for 2 hours and sulfuric acid wasneutralized with sodium methoxide. Methanol was removed by distillationand the residual methyl esters were distilled to obtain a mixture ofcolorless methyl esters, of which 80% was methyl stearate, 5% was methylheptanoate, 15% was dimethyl dodecanedioate. About 1.5 g of blackresidual remained in the distillation flask.

Example 2

This example relates to the separation of 11-aminoundecanoic acid,dodecanedioic Acid, hexylamine, heptanoic acid, and stearic acid fromtheir mixture of sulfuric acid hydrolysis of the mixed amidederivatives.

A mixture of the starting suspension was obtained by hydrolyzing 150 gof the mixed amide derivatives prepared from methyl 12-ketostearateaccording to WO2017/088218 with a mixture of 150 g of sulfuric acid and30 g of water. During the hydrolysis, low-boiling methanol wascontinuously removed.

To the reaction suspension were added 800 g of water and 800 mL oftoluene. The mixture was vigorously stirred for 60 minutes at 85° C. andtransferred to a separatory funnel to separate the two phases.

The toluene phase was treated the same way as in Example 1 and similarresults were obtained for each component.

The aqueous phase was neutralized with aqueous solution of sodiumhydroxide to neutral pH at 7.5 for a total of 115 g of sodium hydroxide.After cooling to 35° C., the crystalline solid was filtered off, washedthree times with deionized water, dried to yield 41.6 g of11-aminoundecanoic acid.

To the mother liquor was added an additional solution of sodiumhydroxide containing 20 g of sodium hydroxide. The solution wasazeotropically distilled with a 2.5×30 cm vacuum jacketed column filledwith porcelain berl saddles until the pH of the overhead became a pH of7-8. The distillate is separated into two phases and the lower aqueousphase was continuously returned to the distillation flask. The crudehexylamine was dehydrated by azeotropic distillation to yield 21.5 g ofhexylamine.

After hexylamine was completely removed, the solution containing sodiumsulfate was treated the same way as in Example 1. An additional 1.2 g of11-aminoundecanoic acid was recovered from the mother liquor.

Example 3

This example relates to the separation of 9-aminononanoic acid, sebacicacid, octylamine, and pelargonic acid.

A mixture of the starting solution was obtained by hydrolyzing 150 g ofthe mixed amide derivatives prepared from methyl 10-ketostearateaccording to WO2017/088218 with 60 g of sodium hydroxide in 800 mL ofwater.

To the turbid solution was added 200 mL of toluene and the mixture wasvigorously stirred at a temperature of 80° C. for 45 minutes.Afterwards, the toluene phase was separated and removed to yield aresidual, which was distilled to obtain 29.5 g of n-octylamine.

The aqueous phase was treated the same way as in Example 1 to obtain36.9 g of pelargonic acid, 39.6 g of 9-aminononanoic acid, and 45.5 g ofsebacic acid.

Example 4

This example relates to the separation of 13-aminotridecanoic acid,brassylic acid, hexylamine, and heptanoic acid.

A mixture of the starting solution was obtained by hydrolyzing 180 g ofthe mixed amide derivatives prepared from methyl ester of14-ketoarachidic acid according to WO2017/088218 with 60 g of sodiumhydroxide in 800 mL of water.

The reaction solution was treated the same way as in Example 1 to yield23.5 g of hexylamine, 29.4 g of heptanoic acid, 53.1 g of13-aminotridecanoic acid, and 62.9 g of brassylic acid.

It will be understood that the foregoing examples, explanation, anddrawings are for illustrative purpose only and that in view of theinstant disclosure various modifications of the present invention willbe self-evident to those skilled in the art and are to be includedwithin the spirit and purview of this application and the scope of theclaims.

What is claimed is:
 1. A process for the separation of long chain aminoacid, dibasic acid, short chain alkylamine, and alkanoic acid of thefollowing structures:

from at least two of them in an acid hydrolysis mixture of the mixedamide derivatives of the following structures:

wherein m is an integer from 0 to 10; n is an integer from 6 to 20; X isOR or NR₁R₂, wherein OR is OH, C₁-C₈ monohydric alcohol, or C₁-C₈polyhydric alcohol, and R₁ and R₂ are each independently hydrogen orC₁-C₈ alkyl group; comprising: (1) adding water and an extractantsolvent to the aqueous suspension of an acid hydrolysis of the mixedamide derivatives to yield an aqueous solution of the acid salt of longchain amino acid and alkylamine and to extract long chain dibasic acid,short chain alkanoic acid, and impurities into the extractant phase; (2)separating the mixture of step (1) into an aqueous phase containing theacid salt of long chain amino acid and alkylamine and an extractantphase containing long chain dibasic acid, short chain alkanoic acid, andimpurities; (3) neutralizing the aqueous phase of step (2) with a basicagent to obtain a crystalline suspension of the long chain amino acid;(4) recovering the long chain amino acid by solid-liquid separation toyield an aqueous mother liquor; and (5) in the extractant phase of step(2), separating the long chain dibasic acid, short chain alkanoic acid,and impurities.
 2. The process according to claim 1, wherein water andan extractant solvent are added to a suspension of the acid salts oflong chain amino acid and alkylamine, dibasic acid, and alkanoic acidconcomitantly, sequentially, continuously, semi-continuously, or batchwise.
 3. The process according to claim 1, wherein the dissolution andextraction are performed at a temperature in the range from 50° C. tothe boiling point of the extractant solvent rich in long chain dibasicacid and short chain alkanoic acid.
 4. The process according to claim 1,wherein the dissolution and extraction are performed at a temperature inthe range from 80° C. to 90° C.
 5. The process according to claim 1,wherein a process for separating alkylamine, inorganic salt, andrecovering long chain amino acid from the aqueous mother liquorcomprises: (a) adding an alkali hydroxide to the aqueous mother liquor;(b) distilling the solution of step (a) or extracting the solution ofstep (a) with an extract solvent to recover alkylamine; (c)concentrating the solution of step (b) to crystallize the inorganic saltand removing the crystallized salt by solid-liquid separation to yield amother liquor; (d) adding an acid to the mother liquor of step (c) toadjust the pH to neutral to precipitate long chain amino acid andrecovering the long chain amino acid by means of solid-liquidseparation; and (e) after recovering the long chain amino acid,returning the mother liquor of step (d) to step (a).
 6. The processaccording to claim 1, wherein a process for separating alkylamine,inorganic salt, and recovering long chain amino acid from the aqueousmother liquor comprises: (a) adding ammonia or ammonium hydroxide to theaqueous mother liquor; (b) extracting alkylamine with an extractantsolvent to yield an aqueous solution containing ammonium salt and asmall amount of long chain amino acid; (c) adding an acid to the aqueoussolution of step (b) to increase the solubility of long chain aminoacid; (d) concentrating the solution of step (c) to crystallize theammonium salt and removing the precipitated salt by solid-liquidseparation to yield a mother liquor; (e) adding ammonia or ammoniumhydroxide to the mother liquor of step (d) to adjust the pH to neutralto precipitate long chain amino acid and recovering the long chain aminoacid by means of solid-liquid separation; and (f) after recovering thelong chain amino acid, returning the mother liquor of step (e) to step(a) or step (c).
 7. The process according to claim 1, wherein the longchain amino acid is precipitated by performing a neutralization reactionof the acid salt with a basic agent at a temperature from 50° C. to 100°C.
 8. The process according to claim 1, wherein the long chain aminoacid is precipitated by performing a neutralization reaction of the acidsalt with a basic agent at a temperature from 70° C. to 80° C.
 9. Theprocess according to claim 1, wherein the long chain amino acid isprecipitated by performing the neutralization reaction of the acid saltwith a basic agent to a pH range from 5 to
 9. 10. The process accordingto claim 1, wherein the long chain amino acid is precipitated byperforming the neutralization reaction of the acid salt with a basicagent to a pH range from 6 to
 8. 11. The process according to claim 1,wherein the long chain amino acid is separated by means of solid-liquidseparation after cooling the crystalline suspension to a temperature inthe range from 30° C. to 40° C.
 12. The process according to claim 1,wherein the extractant solvent is selected from the group consisting ofbutyl formate, isobutyl formate, butyl acetate, isobutyl acetate, propylacetate, isopropyl acetate, ethyl acetate, ethyl propionate, octylacetate, benzene, toluene, xylene, cumene, anisole, diethyl ether,diisopropyl ether, dibutyl ether, methyl tert-butyl ether, ethyltert-butyl ether, methyl tetrahydrofuran, petroleum ether, cyclohexane,dichloroethane, methylene chloride, chloroform, carbon tetrachloride,and trifluoromethylbenzene, n-butanol, isobutanol, amyl alcohol, isoamylalcohol, hexanol, cyclohexanol, 2-ethylhexanol, isooctanol, sec-octanol,butanone, pentanone, hexanone, cyclohexanone, methyl isobutyl ketone,and a mixture of two or more thereof.
 13. The process according to claim1, wherein the extractant solvent is toluene.
 14. The process accordingto claim 1, wherein the basic agent is selected from the groupconsisting of ammonia, alkali and ammonium salts of hydroxide,bicarbonate, carbonate, bisulfite, sulfite, carboxylate, and a mixtureof two or more thereof.
 15. The process according to claim 1, whereinthe basic agent is sodium hydroxide.
 16. The process according to claim1, wherein the long chain amino acids are 9-aminononanoic acid,11-aminoundecanoic acid, or 13-aminotridecanoic acid.
 17. The processaccording to claim 1, wherein the long chain amino acid is11-aminoundecanoic acid.
 18. The process according to claim 1, whereinthe long chain dibasic acids are sebacic acid, dodecanedioic acid, orbrassylic acid.
 19. The process according to claim 1, wherein the longchain dibasic acid is dodecanedioic acid.
 20. The process according toclaim 1, wherein the short chain alkanoic acids are heptanoic acid andpelargonic acid.
 21. The process according to claim 1, wherein thealkylamines are n-hexylamine and n-octylamine.
 22. The process accordingto claim 1, wherein alkali hydroxides are lithium, sodium, potassium orcesium hydroxide.